Known apparatus used for carrying out diagnostics on electronic or electric modules mounted on vehicles consists of diagnostic stations supplied in central areas and permitting carrying out tests in repair stations. These stations are connected to a network of cables arranged first of all in series on the network connecting one module to a given system, and are adapted to calibrate and analyze the status and control signals passing through the network, in order to display on a screen the operating parameters of the given system. The primary disadvantages of these stations come from their very high cost price and the fact that, from their conception, their use is limited to stationary tests. Further, these stations are not adapted to test, during a given division, the totality of state or control signals generated by a module, but only the signals received from a specific element (or transmitted toward this element) connected to the module. The test of all other elements connected to the module requires therefore branching to another network. Further, the only values displayed relate to the measured operating parameters of the vehicle, the interpretation of which requires qualified personnel and the use of very complete repair manuals. Finally, their conception makes very expensive any adaptation to new types of electric or electronic modules.
Diagnostic devices are also known such as that described in European patent EP-A-0.231.607, adapted to be connected by a series connection to specific electronic or electric modules having their own means for treatment of state and control signals which they receive or generate. These units are adapted to deliver calibrated signals to the diagnostic apparatus, via the series connection. Further, the operating parameters displayed are limited to the signals delivered by the units. The function of this diagnostic device is to decode the burst of signals delivered to enable its display. The disadvantage of such devices resides in the fact that their use is limited to electronic or electric modules equipped to deliver a diagnostic raster. Further, the operating parameters displayed are limited to the signals delivered by the modules. Finally, as for the diagnostic stations, the only values displayed concern the measured operating parameters, the interpretation of which necessitates the use of very complete repair manuals.
The present invention seeks to overcome the drawbacks of known devices and has as a first object to provide a low cost diagnostic device relative to prior diagnostic stations, permitting testing of all types of units having, or not having, a diagnostic scanning raster.
Another object of the invention is to permit carrying out full scale road tests.
Another object is to permit detecting and displaying transient defects arising unexpectedly during a road test.
Another object is to provide directly to the operator the interpretation of the defect signal detected and to guide the operator in carrying out the repair.
Another object is to provide an apparatus adaptable at low cost to all new types of modules.